The present invention is concerned with a method of adhering tensioned strips of elastic material to a flexible base material in order to elasticize portions of the base material, and to the elasticized article thereby obtained. The invention finds particular application in elasticizing garments, in particular in elasticizing disposable incontinence control garments, for example, disposable diapers. The manufacture of such articles is usually carried out by joining continuous moving webs of material to form a composite web which is then cut transversely to form the individual articles. It is often desired to elasticize portions of the garments, such as the leg cut-out portions of disposable diapers, in order to provide a snug fit of the diaper about the wearer's legs to aid in controlling or preventing leakage. It is a common expedient in the art to apply bands of elastic material under tension to a moving web or webs of material, utilizing an adhesive, electronic welding, mechanical stitching or any suitable means to secure the tensioned elastic band to the web. Because the elastic band is glued or otherwise secured to the web while held in a tensioned, elongated condition, upon cutting of the web into individual articles the tensioned, elongated elastic bands relax to form elasticized gathers in the flexible material. Generally, any suitable elastic material comprising a suitable rubber, synthetic organic polymeric material or composite material may be utilized as the elastic band.
A particularly useful material for the elastic bands would be one which is both elastic and self-adhering to the flexible base material which is to be elasticized. Such self-adhering elastic material would obviate the need for separate gluing or other securing steps to secure the elastic bands to the flexible base material. Self-adhering elastic materials are known. For example, U.S. Pat. No. 4,259,220 and related U.S. Pat. No. 4,418,123, respectively disclose a viscoelastic, hot melt pressure sensitive adhesive which can be extruded to form a tape which is both pressure sensitive adhesive and elastic, and a method for imparting elastic properties to a flexible substrate by contacting a surface of the substrate with the specified self-adhering elastic material. The disclosure of each of U.S. Pat. No. 4,259,220, issued Mar. 31, 1981 to William L. Bunnelle et al and U.S. Pat. No. 4,418,123, issued Nov. 29, 1983 to William L. Bunnelle et al is incorporated by reference herein.
At least one difficulty exists in utilizing self-adhering elastic materials of the type described in the foregoing U.S. patents to elasticize flexible base materials. This difficulty is that with respect at least to certain base materials such as thin polyolefin sheet material, the greater the degree to which the self-adhering elastic materials are elongated when applied to the base material, the less adherent the self-adhering elastic materials become. In other words, the greater the amount of elongation imposed upon the self-adhering elastic bands applied to the flexible base material, the more the adhesion power of the self-adhering material to the base material is reduced.